I don't think Lance is saying that. It was just part of the bigger picture. Justin wanted to do his own thing and JC and Chris did too from the sound of it. They felt like it was time to break up. Unfortunately, Lance and Joey weren't ready to let it go.
But why didn't they just SAY they wanted to do their own things? Lance wrote that they put the blame on "On The Line". Can you explain why they would use that movie as an excuse to leave, when they could have easily said they all wanted to go solo?